using System;
using System.Collections.Generic;
using System.Linq;

namespace yukicodeX {
    public class Program {
        public static string Solver(System.IO.TextReader reader) {
            var s = MyLib.GetIntList( reader.ReadLine() ).OrderBy( x => x ).TakeLast( 5 ).Take( 4 ).Sum();
            return string.Format( "{0:f2}",  s  / 4.0 );
        }

        private static void Main() {
            Console.WriteLine( Solver( Console.In ) );
        }
    }

    public class MyLib {
        public static string Ordinalization(int num) {
            string surfix = "stndrdth";
            return string.Format( "{0}{1}", num,
                ( 0 < num % 10 && num % 10 <= 4 ) && ( ( num % 100 ) / 10 != 1 ) ?
                surfix.Substring( ( num % 10 - 1 ) * 2, 2 ) : surfix.Substring( 6 ) );
        }

        public static List<int> GetIntList(string input) {
            return input.Split().ToList<string>().ConvertAll<int>( int.Parse );
        }

        public static List<int> GetIntList(string input, char delimitor) {
            return input.Split( delimitor ).ToList<string>().ConvertAll<int>( int.Parse );
        }

        public static List<int> GetIntList(string input, char[] delimitors) {
            return input.Split( delimitors ).ToList<string>().ConvertAll<int>( int.Parse );
        }
    }
}